1. Field of the Invention
The present invention relates to a substrate process method and a substrate process apparatus for heating and drying resist solution on a substrate such as an LCD substrate to be processed before an exposing process and a developing process are performed.
2. Description of the Related Art
When a liquid crystal display (LCD) is fabricated, photoresist solution is coated on a rectangular glass LCD substrate so as to form a resist film. The resist film is exposed corresponding to a circuit pattern. Thereafter, the exposed resist film is developed. Thus, a circuit pattern is formed by photolithography technology.
Before the resist coating process is performed, a hydrophobic process (HMDS process) is performed a rectangular LCD substrate (hereinafter referred to as substrate) in an adhesion process unit so as to improve the adhesiveness of the resist. Thereafter, the substrate is cooled by a cooling unit. The resultant substrate is loaded to a resist coating process unit.
In the resist coating process unit, while the rectangular substrate held on a spin chuck is being rotated, resist solution is sprayed to the center of the front surface of the substrate. The resist solution spreads out on the front surface of the substrate due to centrifugal force of the rotation of the substrate. Thus, the resist film is equally coated on all the front surface of the substrate.
Excessive resist on the periphery of the substrate is removed. The resultant substrate is loaded to a heating process unit. In the heating process unit, a pre-baking process is preformed. In the heating process unit, the substrate is transferred through lift pins and placed on fixed pins of a heating plate and the substrate is heated with heat radiation of the heating plate so as to prevent the substrate from directly contacting the heating plate. This heating method is referred to as proximity method.
Thereafter, the substrate is cooled by a cooling unit. The resultant substrate is conveyed to an exposing unit. In the exposing unit, a predetermined pattern is exposed on the substrate. Thereafter, a developing process and a post-baking process are performed. Thus, a predetermined resist pattern is formed.
However, in the above-described coating and developing processes, after a substrate coated with resist solution is pre-baked or a substrate is exposed and developed, marks of lift pins, fixed pins, vacuum groove, or the like may be transferred to the substrate.
After the pre-baking process is performed, since the film thickness of resist solution coated on the substrate varies corresponding to the marks of the lift pins or the like, the marks of lift pins or the like are transferred. After the exposing and developing processes are performed, since the line width of a circuit pattern formed on the substrate varies corresponding to the marks of the lift pins or the like, the marks of the lift pins or the like are transferred. After the pre-baking process is performed, marks of lift pins or the like may not be present. However, after the developing process is performed, marks of lift pins or the like may be present.
As causes of transfer marks, it is estimated that high sensitivity resist solution has been used in recent years and that the line width of a circuit pattern formed on an LCD substrate is as small as 3:m. However, the causes have not been proved. Thus, technologies for preventing such transfer marks from taking place on a substrate have not been accomplished.
Phenomena of transfer marks show that the film thickness of resist solution coated on a substrate varies corresponding to heat radiation from support pins and proximity pins. After the exposing and developing processes are performed, the line width of a circuit pattern formed on a substrate varies corresponding to heat radiation from support pins and proximity pins. This is because the temperature of support pins and proximity pins is higher than the temperatures of the other portions of the LCD substrate. In contrast, the temperature of the vacuum groove is lower than the temperatures of the other portions of the LCD substrate. Since transfer marks are present on products, product defects take place.
However, as described above, since transfer marks of lift pins or the like take place due to unevenness of film thickness of a resist film and fluctuation of line width of a circuit pattern, it is necessary to prevent such transfer marks from taking place on an LCD substrate in the coating and developing processes. Moreover, in high sensitivity resist that will be widely used, when resist is not completely dried after the resist coating process is performed until the exposing process is performed, the resist that has not been dried dissolves in developing solution. Thus, the line width of the circuit pattern will vary.